One of the most powerful techniques for separating genetic and environmental influences on intelligence and personality functioning is the adoption method. The adoption method disentangles these influences by studying children who have not been reared by their biological parents, but this method has been used only rarely because of difficulties in obtaining adequate measures on biological parents. The proposed study seeks to follow the offspring of 1468 girls who routinely were administered intelligence and personality tests while awaiting the birth of their child in a home for unwed mothers. Their children, now aged one to 16 years, were placed into adoptive homes shortly after birth and most of the addresses of their adoptive parents are known. The intention is to test the adoptive parents and their adoptive and natural children (20 percent of the adoptive families have biological children of their own, and 50 percent have more than one adoptive child) on a variety of intellectual, personality, and child-rearing measures. By comparing biological mother-child correlations with adoptive parent- child correlations, it will be possible to estimate the relative influence of genes and environment on the intellectual and personality characteristics measured. The large sample size will permit not only one of the most reliable estimates so far of genetic and environmental influences on intelligence and personality, but will also allow a variety of quasi-experimental designs to be applied to estimates of the "reactive range" on these traits. One such design can evaluate the fate of children of high or low IQ mothers reared in adoptive homes with parents of similar or different IQ.